In starting courses laid over foundations, bed joints must be within which thickness range?

• A. 1/2 inch
• B. 3/4 inch
• C. 1 inch
• D. 5/8 inch

Answer: (B)

Starting courses over foundations need a bed joint thick enough to bridge small irregularities in the base and provide a solid, level footing for the first row. A bed joint of about three-fourths of an inch gives that forgiving bedding: it fills minor voids, helps the first course sit evenly, and creates a strong initial bond. If the joint is thinner, around half an inch, gaps may not fill properly and the bond can be weaker. If it’s much thicker, like one inch, too much mortar can squeeze out, waste material, and make it harder to keep the courses true. Three-fourths of an inch strikes a practical balance for a stable, true starting course.